Stress Reduction in Multilayers Used for X-Ray and Neutron Optics

Abstract

Multilayer systems have important applications in many areas of X-ray and neutron optics. For some applications the positions of the optical surfaces have to be controlled with accuracies in the sub-nanometre range. For neutron supermirrors with over a thousand layers, stresses above 1000MPa can occur. In addition to bending the substrate such stresses can lead to the films peeling from the substrate, or even to the destruction of the substrate surface, and so must be avoided. After an introduction to stress, this chapter describes how stresses can be reduced to acceptable values and discusses two examples – FeCo/Si polarizing neutron supermirrors and Mo/Si multilayer mirrors for extreme ultraviolet lithography.